Hola Richard

When comparing an abstract idea or an indefinite amount, Spanish often uses "más de." In this case, "lo que quería" (what I wanted) is an abstract idea. 

We are still seeing that second element of the sentence as an amount of something but referring to something uncountable like an idea. The sentence doesn't explicitly says what they "received" or what they "wanted", they could be talking about money, letters... or more abstract ideas like care, understanding, support... - but whichever it is we are still talking about some "quantity".  It's common in Spanish to use this construction for comparing expectations or abstract amounts to reality. The sentence "Obtuve más que lo que quería" sounds a bit awkward because "más que" is not typically used to compare abstract ideas or quantities in this manner.

Interesting question. 

Gracias y saludos